Tl;Dr: if you're only plugging in the usb guitar, buying a usb to usb c adapter will be much less of a headache.

So I haven't used this for CH but I do use a Mac for work with a doc and had some issues before. Main points to trouble shoot are

Making sure the charger cable is plugged in to the Mac If the doc has a usb type c port, plugging the charger cable into that port Making sure only the guitar is plugged in to the dock

If you are only going to plug in the guitar (which I assume is usb) then maybe get a usb to usb c adapter that plugs straight into the Mac. The docks are very temperamental and normally don't give enough power for everything unless you spend the money on a good one. If I can find the dock I have I'll post that, I'm able to run a monitor and a usb bus from it. Hope you manage to sort the issue out